Preparation of heavy metal cyclopentadienides in the presence of a non-benzenoid nitrogen base



Patented Oct."9, 1962 nice PREPARATIGN OF HEAVY METAL CYCLQPENTA-DIENIDES IN THE PRESENCE OF A NON-BEN- ZlENQID NETRQQEN BASE Eddie G.Lindstrom, Richmond, Califi, assignor to (California ResearchCorporation, San Francisco, Calif., a corporation of Delaware NoDrawing. Filed Sept. 3, 1954, Ser. No. 454,233

9 Claims. (ill. 260-439) This invention relates to a unique anduniversal method of preparing metal cyclopentadienides, and isparticularly applicable to the preparation of the metalbiscyclopentadienyls, illustrative of which is iron biscyclopentadienyl.

The metal biscyclopentadienyls have been recently developed as a uniqueclass of organometallic componds. Starting with ironbiscyclopentadienyl, commonly referred to as ferrocene, this class ofnovel compounds has gradually been expanded through the efforts ofnumerous investigators to include corresponding-type compounds oftitanium, chromium, manganese, cobalt, nickel, ruthenium, tin and lead.A number of methods of preparing individual members of this class ofcompounds has been reported, the majority of which are restrictive intheir application and are peculiar to the preparation of one or moreisolated members of the metal biscyclopentadienyls. In contrast to therestrictive nature of these reported methods of preparation, a uniquereaction process has now been found which may be applied universally tothe preparation of this class of compounds.

According to the present invention, the metal cyclopentadienides may beprepared by the liquid phase reaction of a compound containing acyclopentadiene nucleus and possessing a reactive acidic hydrogen in thecyclopentadiene nucleaus, such as cyclopentadiene, thealiphatic-substituted derivatives of cyclopentadiene or polynuclearcompounds containing a reactive cyclopentadiene nucleus, with ananhydrous metal salt and, preferably, a tdivalent'heavy metal salt whenconducted in the presence of a nonbenzenoid nitrogen base having a basicdissociation constant (K greater than 1X10- The conduct of this processmay be best understood by reference to its application in thepreparation of the iron cyclopentadienides and particularly ironbiscyclopentadienyl.

In this reaction, the iron reactant may be introduced in the form of aferric or ferrous salt of an organic or inorganic compound containingareplaceable and acidic hydro gen, provided the reactant is introduced ina substantially anhydrous form. Examples of suitable iron compounds arethe halides, sulfates, nitrates, acetates, acetonylacetates, formates,propionates, etc., of which the halides, acetates and formates arepreferred. Additionally, it is preferable to employ the iron salt in theferrous form, such as ferrous chloride.

The organic reactant of the process may be cyclopentadiene or its dimer,as well as substituted cyclopentadiene or polynuclear compounds, such asindene, which contain a cyclopentadiene nucleus and an acidic andreplaceable hydrogen on the cyclopentadiene nucleus. The substitutedcyclopentadienes are those containing one or more aliphatic substituentsattached to the cyclopentadiene nucleus and, preferably, thealkyl-substituted cyclopentadienes in which the alkyl radicals containfrom 1 to 5 carbon atoms. Other substituent groups may be incorporatedin the cyclopentadiene nucleus provided such substituent groups areinert to the process reactants and provide no hindrance to the formationof a cyclopentadiene anion.

Of critical importance to the conduct of the process is the presence ofa nonbenzenoid nitrogen base possessing a basic dissociation constant (Kgreater than 1X10? Aside from the limitations on the K of these nitrogenbases, compositionwise, they include ammonia; the primary, secondary andtertiary aliphatic amines, such as the alkyl amines and alkanol amines;and the N-heterocyclic compounds corresponding to the cycloaliphatic orsaturated ring structures. These nonbeneznoid nitrogen bases, bydefinition, should be liquid at the temperature and pressure at whichthe reaction is conducted. As specific illustrations of the class ofnonbenzenoid nitrogen bases falling within the scope of the foregoingdefinition may be mentioned the following: ammonia (K 1.8 10- secondarybutylamine (K 4.4 10- diethylamine (K 1.26 10- diisoamylamine (K 9.6 10diisobutylamine (K 4.8 10- dimethylamine (K 5.2 l0 dipropylamine (K1.02. 10- ethylamine (K 5 .6 '1 0 ethylenediamine (K 8.5 X 1Oisoamylamine (K 5 10* isobutylamine (K 3.1 10- isopropylamine (K 5.3 10-methylamine (K 5 10- methyldiethylamine (K 2.7 X10 piperidine (K 1.6x10- u-propylamine (K, 4.7 10- tetramethylenediamine (K 5.1 X 10-triethylamine (K 6.4 10- triisobutylamine (K 2,6 10- trimethylamine (K7.4x 10 trimethylenediamine (K 3.5 X 1O tripropylamine (K 5.5 X10 etc.It has been found that, directionally, the greater the K of the nitrogenbase, the higher the yield of desired cyclopentadienide.

In general, the temperatures of the reaction have not been foundcritical, although, directionally, higher yields of cyclopentadienideproduct have been obtained with increasing temperatures of reaction. Thereaction is conducted in the liquid phase so that the reactiontemperatures should be maintained substantially below the boiling pointof the reactants. Pressure vessels may sometimes be employed to maintainthe reaction system in a liquid state. It is preferable to operate atreasonably low temperatures to avoid excessive polymerization andcorresponding loss of the cyclopentadiene reactant. In gen eral, it isdesired to conduct the reaction process at temperatures in the range of20 to 200 C., with the preferred range of operation between 40 and C.

In the operation of the process, it is desired to employ the metalreactant and the cyclopentadiene reactant in approximatelystoichiometric ratio, e.g., approximately 2 mols of cyclopentadienereactant per mol of metal reactant. The nonbenzenoid nitrogen base ispreferably employed in molar excess quantities, e.g., at least 1 mol ofnitrogen base per mol of cyclopentadiene reactant.

The exact mechanism of the reaction involved in the subject process hasnot been conclusively determined, although it appears that the nitrogenbase may have a primary and secondary function as both a reactioncomponent and a solvent. In some cases, the invention process may beadvantageously carried out in the presence of a hydrocarbon solventsubstantially immiscible with the nitrogen base. The function of thishydrocarbon solvent would be to remove the reaction product from thereaction zone as it is for-med. A particularly desirable solvent wouldbe the alkanes and aromatic hydrocarbons.

The resulting iron cyclopentadienides may be recovered from the reactionsystem by a number of conventional methods, depending upon the physicalcharacteristics and stability of the product. The metalcyclopentadienides will range from solid to liquid and very reactive toextremely stable, The highly reactive cyclopentadienides have been foundextremely susceptible to the presence of oxygen and decompose even byusing stable oxygen-containing solvents. The solid products, such as themetal biscyclopentadienyls and, particularly, iron biscyclopentadienyland the lower alkyl-substituted derivatives, may be sublimed from thereaction mixture after removal of the liquid components.

Example Ms mol (16 grams) of anhydrous ferrous chloride was dispersed in150 milliliters of piperidine (K 1.6 10 5 mol (20 grams) ofcyclopentadiene was added and the mixture was stirred and heated at areaction temperature of 80 to 100 C. for three hours. The reactionmixture was cooled, quenched with water, and the product was extractedin ether. The resultant ether extract was washed once with dilutehydrochloric acid and twice with water. The ether was then removed fromthe reaction product under vacuum in a boiling water bath. The residueconsisted of crude iron biscyclopentadienyl which was obtained in ayield of 57 percent by weight.

The foregoing reaction was duplicated in further experiments at varyingreaction temperatures and employing diiferent nitrogen bases as thereaction component. Thus, iron biscyclopentadienyl was recovered invarying yields when employing diethylamine, triethylamine, n-butylamineand monoethanolamine at reaction temperatures varying between 40 to 75C.

When employing ammonia as the nitrogen base and conducting the reactionat liquid ammonia temperatures of 33 C., no yields of ironbiscyclopentadienyl were obtained. However, when conducting the reactionwith ammonia under pressure in an autoclave at a reaction temperature of80 C., the reaction was found to proceed with formation of appreciableyields of iron biscyclopentadienyl.

Additional experiments employing an aromatic amine, such as benzylamine(K 2.0 10 at temperatures of 60 to 90 C., failed to result in yields ofrecoverable iron biscyclopentadienyl. Also, experiments with nitrogenbases possessing a K less than 1x10 as exemplified by diethanolamine (K5 10 also failed to produce the desired product.

Obviously, many modifications and variations of the invention, ashereinbefore set forth, may be made without departing from the spiritand scope thereof, and therefore only such limitations should be imposedas are indicated in the appended claims.

I claim:

1. A process for the production of divalent heavy metalcyclopentadienides which comprises reacting in the liquid phase acyclopentadiene compound containing a reactive acidic hydrogen in thecyclopentadiene nucleus with an anhydrous divalent heavy metal salt inthe presence of a nonbenzenoid nitrogen base having a basic dissociationconstant greater than 1 10- 2. A process for the production of an ironcyclopentadienide which comprises reacting in the liquid Phase acyclopentadiene compound containing a reactive acidic hydrogen in thecyclopentadiene nucleus with an anhydrous iron salt in the presence of anonbenzenoid nitrogen base having a basic dissociation constant greaterthan 1 x 10" 3. A process for the production of an ironcyclopentadienide which comprises reacting in the liquid phase acyclopentadiene compound containing a reactive acidic hydrogen in thecyclopentadiene nucleus with an anhydrous ferrous salt in the presenceof a nonbenzenoid nitrogen base having a basic dissociation constantgreater than 1 X10? 4. A process for the production of an ironcyclopentadienide which comprises reacting in the liquid phase analiphatic-substituted cyclopentadiene with an anhydrous ferrous salt inthe presence of a nonbenzenoid nitrogen base having a basic dissociationconstant greater than 1 X 10? 5. A process for the production of ironbiscyclopentadienyl which comprises reacting in the liquid phasecyclopentadiene with an anhydrous ferrous salt in the presence of anonbenzenoid nitrogen base having a basic dissociation constant greaterthan 1 X10- 6. A process for the production of an iron cyclopentadienidewhich comprises reacting in the liquid phase a cyclopentadiene compoundcontaining a reactive acidic hydrogen in the cyclopentadiene nucleuswith an anhydrous ferrous salt in the presence of piperidine.

7. A process for the production of iron biscyclopentadienyl whichcomprises reacting in the liquid phase cyclopentadiene with an anhydrousferrous salt in the presence of piperidine.

8. The process for the production of the dicyclopentadienide of adivalent transition metal which comprises reacting the dihalide of saidmetal with cyclopentadiene in a liquid phase under anhydrous conditionsand in the presence of piperidine.

9. The process for the production of the dicyclopentadienide of adivalent transition metal which comprises reacting the dihalide of saidmetal with cyclopentadiene in a liquid phase under anhydrous conditionsand in the presence of an N-heterocyclic compound having a basicdissociation constant greater than 1x10 References Cited in the file ofthis patent Birmingham et al.: Journ. Am, Chem. Soc., Vol. 76, Aug. 20,1954, p. 4179.

Fischer et al.: Fur Naturforschung; Vol. 8B, #5 pp. 217-219, May 1953.

Fischer et al.: Zeit. Fur Naturforschung; Vol. 8B, #6, pp. 327-328, June1953.

Wilson et al.: Chemical Reviews, Vol. 34, No. 1, pp. 34 and 35, February1944.

Wilkinson: Jour, Am. Chem. Soc., Vol. 76, pp. 209- 211, Jan.5, 1954.

Wilkinson et al.: Chem. and Ind., March 13, 1954, pp. 307-308.

1. A PROCESS FOR THE PRODUCTION OF DIVALENT HEAVY METALCYCLOPENTADIENIDES COMPOUND CONTAINING A RELIQUID PHASE ACYCLOPENTADIENE COMPOUND CONTAINING A REACTIVE ACIDIC HYDROGEN IN THECYCLOPENTADIENE NUCLEUS WITH AN ANHYDROUS DIVALENT HEAVY METAL SALT INTHE PRESENCE OF A NONBENZENOID NITROGEN BASE HAVING A BASIC DISSCOIATIONCONSTANT GREATER THAN 1X10-5.